public class zuheshu {
    public static void main(String[] args) {
        int [] C = new int [2];
        int sum,i;
        for(i=0;i<args.length;++i) {
            C[i] = Integer.parseInt(args[i]);
        }
        sum = diedai(C[0],C[1]);
        if(sum == 0)
            System.out.println("组合数错误");
        else
            System.out.println(sum);
    }
    public static  int diedai (int n,int m) {
        if(m==1)
            return n;
        else if(m==0||m==n)
            return 1;
        else if(n<m||n==0)
            return 0;
        else
            return diedai(n-1,m-1)+diedai(n-1,m);
    }
}

